Conventionally, antenna devices are known that include a radiation unit (an antenna element) for radiating an electromagnetic wave, and a dielectric body for beam-forming the electromagnetic wave radiated from the radiation unit. JP2008-028795A and JP2010-157865A disclose such antenna devices.
The conventional radiation unit includes, for example, a waveguide formed with slits, and the electromagnetic wave is radiated from the slits. A plurality of dielectric bodies are arranged on an electromagnetic wave radiating side of the radiation unit. The electromagnetic wave radiated from the radiation unit is beam-formed according to, for example, a shape or an arrangement of the dielectric bodies.
For example, by arranging two of the dielectric bodies to face each other at a predetermined distance so that the electromagnetic wave passes therebetween, a beam width of the electromagnetic wave can be suppressed.
Incidentally, an antenna having a long length of, for example, several meters, may be used as a slot array antenna for a ship. When applying the dielectric body to this kind of antenna, a long dielectric body is required. However, because a long dielectric body is higher in cost per length unit compared to a shorter dielectric body, material costs increase. Moreover, a long dielectric body is difficult to handle since, for example, transportation costs increase, and time and labor required for assembly increase.
In order to solve this problem, instead of utilizing the long dielectric body, a configuration of arranging a plurality of the shorter dielectric bodies in a row can be considered. However, in this configuration, a boundary (divided face) between the adjacent dielectric bodies becomes a wave source, and causes side lobes. As a result, for example, a false image is displayed on a radar image, and a proper transception of the electromagnetic wave cannot be performed.
The present invention is made in view of the above situation, and provides an antenna device including a plurality of dielectric bodies, configured to suppress an effect of the boundary between the adjacent dielectric bodies becoming a wave source and causing side lobes.